It is highly desirable and beneficial to provide pressure operated cartridge containers of the type used for storing and dispensing diverse products such as, sealants, adhesives, or lubricants and the like, and commonly known in the industry as a caulking cartridge, with an improved interior nozzle opening closure seal that includes a pressure activated self opening feature.
These types of containers can be constructed of diverse materials such as plastic, paperboard, or metal, or combinations of one or more of the above. They generally consist of a hollow cylindrical tube sealed at one end by a sliding interior piston, with an opposite end sealed by a wall end that incorporates a hollow plastic exterior dispensing nozzle with an interior opening in its base.
To dispense the contents the cartridge is loaded into an application gun comprised of a central body portion with one end forming a fixed perpendicular wall end that butts up against and holds the nozzle end of the cartridge. The opposite end of the gun incorporates a handle with a trigger that advances a mounted plunger into the bore of the cartridge when squeezed, thereby engaging and advancing the sliding interior piston which pressurizes the cartridge and forces the contents out through the dispensing nozzle.
Because the bore of these plastic cartridge nozzles generally taper to a point, filling equipment is usually unable to completely fill the dispensing nozzle with the container material, leaving an air pocket in the nozzle. Certain types of contained products when exposed to even a small amount of air can dry out in the cartridge and become unusable. Other types of contained products can be adversely affected when coming into contact with the plastic of the nozzle itself and require a metallic lined cartridge with a metal end cap and piston to maintain product usability. To overcome these drawbacks manufacturers added a metal foil seal that is bonded over the interior opening of the nozzle and is very effective in preventing the cartridge contents from being ruined by coming into contact with the plastic nozzle or any air trapped inside.
In order to dispense the cartridge contents, the user is required to follow three procedures. First, the cartridge is loaded into the application gun. Second, the nozzle has to be opened by cutting off the tip. And third, the foil seal inside the base of the nozzle has to be pierced to allow the cartridge contents to dispense out through the nozzle opening when the cartridge is pressurized.
The first two procedures are straight forward and easily accomplished, however, the third procedure is not. The user is required to provide a rod shaped tool that has to be thin enough to insert into the nozzle opening, long enough to reach the foil seal, and then be strong enough to pierce it. This rod tool is not supplied with the cartridge. There are a number of disadvantages to this, such as; not having a tool available; if a thin bead of material is needed an oversized tool will stretch out the smaller opening of the tip when inserted into the nozzle; forgetting to pierce the seal and over pressurizing the cartridge to the bursting point which could be quite dangerous to the user; wasting time having to locate or fashion a piercing tool; the piercing tool becomes covered with sticky uncured material after each use and must be cleaned or discarded, or if the tool is thin the seal must be pierced numerous times to provide a large enough opening in the seal for the material to flow out properly.
These disadvantages are well recognized and could be effectively eliminated by providing a leak proof self opening frangible seal for the interior opening of the nozzle that is both, sufficiently strong enough to remain intact from the internal pressure created in the cartridge during the filling operation, and, at the same time, sufficiently weak enough to allow the seal to fail and burst open from the additional pressure that can be brought to bear against the seal when the cartridge is pressurized by the application gun.
There have been several prior art patents granted for self opening cartridge type containers that offer similar and differing design solutions, materials and methods in attempting to provide this feature.
U.S. Pat. No. 2,646,906 to Jones describes a frangible cartridge nozzle seal comprised of a layer of polyethylene that is bonded over the nozzle opening. The seal bursts open in an undefined configuration when sufficient container pressure is created by advancing the interior piston of the cartridge with the application gun.
U.S. Pat. No. 3,029,987 to Gronemeyer describes a plastic cup shaped frangible sealing device that is inserted into the base of the nozzle and held by a flange. The partition wall end of the cup contains various scored v shaped groove configurations forming weakened sectors that rupture when sufficient container pressure is created by advancing the interior piston of the cartridge with the application gun.
U.S. Pat. No. 3,071,294 to Galbierz describes a frangible cartridge nozzle seal comprised of a layer of metal foil with a layer of polyethylene adhesive applied that allows the seal to be bonded over the nozzle opening and the seam where the nozzle flange joins the wall end cap of the cartridge. The seal bursts open in an undefined configuration when sufficient container pressure is created by advancing the interior piston of the cartridge with the application gun.
U.S. Pat. No. 6,578,737 to Jackman describes a cartridge nozzle seal comprised of foil that is burst open by being stretched and forced into cutting serrations located at the base of the dispensing nozzle when sufficient container pressure is created by advancing the interior piston of the cartridge with the application gun.
Each of these prior art patents present differing drawbacks in their method of operation, functionality, or the materials used such as; the use of a single layered polyethylene seal that bursts open in an undefined configuration when the cartridge is pressurized offers no provision for the possibility that seal material may break off and contaminate the contents of the cartridge when dispensed, such as described in U.S. Pat. No. 2,646,906 to Jones. The use of a cup shaped seal that is inserted into the nozzle and bursts open in the configuration of weakened grooves when the cartridge is pressurized requires an additional part that adds to the cost and complexity of the cartridge, such as described in U.S. Pat. No. 3,029,987 to Gronemeyer. The use of a single layer metal foil seal with a layer of adhesive that bursts open in an undefined configuration when the cartridge is pressurized offers no provision for the possibility that seal material may break off and contaminate the contents of the cartridge when dispensed, or that the burst pressure of the seal may vary beyond acceptable limits from inconsistencies formed in the adhesive layer from being heated during its installation, such as described in U.S. Pat. No. 3,071,294 to Galbierz. The use of a single layer metal foil seal with a layer of hot melt adhesive that bursts open when the seal is stretched and forced into serrated cutters at the base of the nozzle offers no provision for controlling the burst pressure of the seal which is determined by the tension left in the seal when the hot melt adhesive and metal foil cools which may cause the seal to prematurely burst from having too little tension to remain intact during the filling operation or from having too much tension that would cause the seal to burst at a pressure that is beyond acceptable limits, such as described in U.S. Pat. No. 6,578,737 to Jackman.
Consequently, a need still exists for a cartridge closure seal that overcomes the aforementioned drawbacks inherent in the prior art. The advantages of my invention include features such as, but not limited to; the ability to precisely control the burst pressure of the seal, the ability of the seal to retain any broken material when the seal bursts; its low cost; and its compatibility with existing cartridges, manufacturing equipment and methods. These and other features and advantages of my invention will become more readily apparent to those skilled in the art by a reading of the detailed description of the device when done in conjunction with the drawings shown in the illustrated embodiments of the invention.